Catamenial tampon and method

ABSTRACT

A catamenial tampon incorporating an absorbency improving agent which is a cross-linked polyacrylamide in which part of the amide groups have been hydrolyzed to carboxylate groups is disclosed. The additive is characterized by a high degree of absorptiveness and remains tack-free throughout its absorptive range. A method of making the tampon is also disclosed.

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bency improving agent which is a cross-linked polyacrylamide in which part of the amide groups have been hydrolyzed to carboxylate groups is disclosed. The additive is characterized /32 on y 2:1 1 A [51] lnt.Cl............. [50] by a high degree of absorptiveness and remains tack-free throughout its absorptive range. A method of making the tampon is also disclosed.

[56] References Cited UNITED STATES PATENTS 12/1961 Leupold and the cross-linking units:

CATAMENIAL TAM PON AND METHOD This invention relates to catamenial tampons and more particularly to an improved high-absorbency tampon, as well as to 1 methods of making such a tampon. I

Catarnenial tampons are commonly made by compressing into cylindrical form a rectangular pad of cellulosic fibers, especially long staple cotton fibers. Such fibers have a natural resilience, absorbency, and length which make them particularly suitable for use in such a compressed tampon. The fiber resilience promotes expansion of the tampon when it is wetted to open up the fiber mass, thereby drawing fluids into, and holding them in, the spaces between the inner fibers of the tampon by wetting and capillary action.

It is manifestly desirable that a catamenial tampon have a high degree of absorbency. The absorbency of such a tampon depends to some extent on such factors as fiber composition and density. However, it has been found that only a relatively small improvement in absorbency, of the order of say 5 to percent, can be obtained by varying fiber composition and density. To achieve more substantial increases in absorbency it is necessary to incorporate an absorbency-improving additive in the tampon.

In order to be suitable for use in tampons an absorbency improver must not only produce a substantial increase in absorbency but also satisfy a variety of other requirements. Thus it should be substantially insoluble, nontoxic and obtainable at a reasonable cost. It should be capable of absorbing substantial quantities of fluids without adversely affecting the integrity of the tampon, i.e., it should stay the dimensional confines of the tampon throughout its absorptive range. Also it should be capable of passing completely through its absorptive range without developing a tackiness or adhesiveness that would cause it to adhere to moistened tissue.

Various known thickening and gelatinizing agents have previously been proposed for use in tampons. However, those 1 agents that have been shown to produce a substantial increase in absorbancy have failed to meet one or more of the other requirements outlined above.

It is accordingly an object of the present invention to provide a tampon comprising compressed cellulosic fibers having incorporated therein an absorbency-improving additive which not only produces a substantial increase in the fluid absorbency of the tampon, but also meets the individual and several additional requirements set forth above. It is another object of Wherein R is hydrogen or lower alkyl such as methyl or ethyl,

. Y is Nl-i or M0, and M is an alkali metal such as sodium, potassium, or lithium, or ammonium. Preferably about 20 to t 40 percent of the amide groups represented by Y" are variety of ways. Thus the polymer in dry powder form may be distributed in a pad of absorbent cellulosic fibers, e.g., cotton, as by dusting in the powder. A water spray may be used, if desired, to secure the powder to the cellulosic fibers and the pad dried before being compressed into a tampon. Alternatively, the polymer may be applied to thin layers of nonwoven fabric in any of various ways and the treated layers of nonwoven fabric interleaved with layers of cellulosic fibers to form a laminar pad that is compressed to a tampon.

Nonwoven fabrics are commonly made of cellulosic fibers, e.g., 20 percent cotton and 80 percent rayon. They may be made from card webs or random (air blown) webs. in either case the fibers of the web are usually bonded by application thereto of a small amount of fluid adhesive and subsequent heat curing of the adhesive to provide the web with the neces' sary integrity so that it can be handled and used. The web is usually wet with water prior to bonding, and the bonding agent, e. g., an acrylic latex emulsion, applied thereto by spraying or by a rotary applicator, followed by a conventional heat cure.

The polyacrylamide additive of the invention may be applied to the nonwoven web during manufacture thereof. Thus the polymer in granular form may be applied to the wetted web prior to or after application of the bonding agent thereto by means of a vibrating feeder or other suitable distributing device and the web passed through a drum dryer to cure the 5 bonding agent and affix the polymer to the web. The polymer the invention to provide a tampon containing a high-absorbency additive that remains substantially tack-free throughout its entire absorptive range. It is still another object of the invention to provide a method of making such a tampon. Other objects of the invention will be in part obvious and in part pointed out hereafter.

The present invention is predicated on the discovery that the foregoing objects can be achieved by using as the absorbency-improving additive in a tampon a polyacrylamide copolymer formed by polymerizing an acrylamide with N,N- methylene bisacrylamide to form a cross-linked copolymer and subsequently hydrolyzing a portion of the amide groups of the copolymer. The resulting copolymer consists essentially of the linear units: F- R may be applied to the extent of say 30 to 60 percent by weight of the web. Alternatively, the additive may be applied to the prebonded web in the form of an aqueous gel or slurry in a suitable liquid carrier and the web thereafter heated to remove the liquid-dispersing medium and affix the polymer to the web.

While a nonwoven web of the type referred to above is a preferred support medium for the polyacrylamide additive, other types of supports such as fiber gauze, scrim or porous paper may also be used. Furthermore, the polyacrylamide polymer may be formed into a film and interleaved with layers of cotton without a separate support. In cases where the polymer is used in fiber form, it can be carded or otherwise incorporated into the cotton used to form a tampon, or into a nonwoven web that is interleaved with iayers of cotton.

In order to illustrate the absorbency that can be obtained by using the present polyacrylamide polymer, a series of tampons was prepared containing various amounts of the polymer and their absorbencies were compared with those of similar tampons containing no additive.'The tampons were prepared by splitting open individual cotton pads of the type from which tampons are normally compressed and manually dusting onto both interior surfaces a preweighed amount of the additive. The pads were then reassembled, pressed into tampons and the absorbency of the tampon determined. The results are given in the table below wherein the units of the numerical values set forth are grams.

- From the foregoing table it is apparent that the present additive, when incorporated in a tampon, is capable of increasing the absorbency of the tampon by as much as 80 percent or more. Moreover, relatively small amounts of the additive produce quite substantial increases in absorbency. As a practi cal matter the quantity of additive should, in most cases, desirably be in the range 2 to 15 percent of the weight of the tampon.

In a second series of tests the same procedure was followed except that a water spray was used to improve the bonding of the polymer ganules to the cotton pads, and the pads werev then dried before being assembled and compressed into a tampon. The results of the absorbency tests on these tampons were essentially the same as those given in the above table.

ln addition to providing good absorbency, the present additive is insoluble in aqueous fluids and nontoxic. Moreover, it

remains tack-free throughout its absorbency range; it passes from the dry state to the saturated state, wherein it has absorbed of the order of 600 to 800 times its weight of water,

without becoming adhesive.

In this specification and the accompanying drawings we have shown and described a preferred embodiment of our invention and have suggested various alternatives and modifications thereof; but it is to be understood that many other changes and modifications can be made within the scope of the invention. These suggestions herein disclosed are selected and included for purposes of illustration, in order that others skilled in the art will be able more fully to understand the invention and principles thereof and will thus be enabled to modify it and embody it in a variety of forms, each as may be best suited to the conditions of a particular use.

Referring now to the accompanying drawing which illustrates a tampon incorporating a preferred embodiment of the invention:

FIG. 1 is an exploded perspective view of a laminar pad adapted to be used in forming a tampon;

FIG. 2 is a perspective view, on a smaller scale, of the pad of FIG. 1 with an overwrap applied thereto; and

FIG. 3 is a side view on a larger scale of a tampon formed from the pad.

Referring to FIG. 1, the numeral generally indicates a rectangular laminar padcomprising the layers 12 of long staple cotton and the interleaved layers 14 of nonwoven fabric. The fabric layers have applied thereto by one of the methods outlined above about 50 percent by weight, based on the weight of the fabric layer, of a polyacrylamide polymer (Down Chemical Co. NC 1336) responding to the structural formula given above when R" is hydrogen and about 35 percent of the amide groups represented by Y have been converted to potassium carboxylate groups.

As shown in the drawing the cotton fibers of the layers 12 are oriented in a direction substantially transverse to the long dimension of the pad. The number of layers used in forming the pad may be varied as desired. Pads of the type illustrated in FIG. 1 can be conveniently made by preparing long strips of long staple cotton-of suitable width, say 4 inches, with the fibers generally oriented lengthwise of the strip and long strips of the polymer-impregnated nonwoven fabric of the same width. The cotton and nonwoven strips are then interleaved to form a laminar structure which is cut at intervals of say 1% inches to form laminar pads of the type illustrated in FIG. 1.

Referring to FIG. 2, in order to improve the integrity of the tampon it is usually desirable, although not essential, to encase the pad in an overwrap 16 that is highly pervious to liquids.

The overwrap is advantageously made from one of the adhesive-bonded, nonwoven, cotton or cotton-rayon fabrics which are relatively inexpensive and yet attain a surprising degree of wet-strength due to the bonding. An example of this type of overwrap fabric is the Kendall Company's Webril" fabric, a 7

nonwoven fabric which is bonded along spaced lines, e.g., in a printed zigzag pattern, with an acrylic resin. For use on a tampon, the bonding may be made with an adhesive having an attractive contrasting color to alert the user to the presence of the overwrap, which might otherwise be nearly invisible on tampon, except on close inspection, thereby giving the user visual assurance of its presence. The overwrap can be made alternatively from any of a number of commercial liquid-pervious fabrics, for example, gauze, knitted, leno-weave, apertured nonwoven etc.

As shown in FIG. 2 the overwrap is wrapped around the pad 10 to form an envelope and held in place by a series of stitches 18 which extend along the longitudinal centerline of the pad. As indicated in FIG. 2, the stitches 18 can be conveniently used to secure a conventional withdrawal cord 20 to the pad.

After completion of the assembly shown in FIG. 2, the pad and overwrap are laterally compressed to form the cylindrical tampon 22 shown in FIG. 3. Due to the transverse orientation of the fibers of layers 12 and the lateral compression of the pad, relatively large number of free fiber ends are located at the cylindrical surface of the tampon. This endwise orientation of the fibers at the tampon surface substantially facilitates induction of liquid into the tampon. After the tampon is formed it is desirably encased in the usual telescopic applicator as shown, for example, in Haas US. Pat. No. l.926,900.

From the foregoing description it should be apparent that the present invention provides a catamenial tampon capable of achieving the objectives set forth above. By incorporating loss and the cross-linking units:

wherein R is hydrogen or lower alkyl and about one-third of 0 said Y" groups are K0- and the remainder NH,, said additive being present to the extent of 2 to 15 percent of the weight of said tampon.

2. A catamenial tampon comprising compressed cellulosic fibers having incorporated therein an absorbency improving additive which is a cross-linked polyacrylamide consisting easentially of the linear units:

f OIL-C andthe cross-linking units:

til

a. A tampon according to claim 1 wherein about 20 to 40 percent of the Y groups are MO groups and the remainder are NH, groups.

4. A tampon according to claim 3 wherein M is potassium.

5. A tampon according to claim 2 wherein said additive is dispersed in said cellulosic fibers in powder form.

6. A tampon according to claim 2 wherein said additive is dispersed in said cellulosic fibers in fiber form.

7. A tampon according to claim 2 wherein said tampon is formed of laminations of cellulosic fibers and nonwoven fabric and said additive is incorporated in the nonwoven fabric.

8. A tampon according to claim 2 wherein said additive is present to the extent of 2 to 15 percent by weight of said tampen.

9. A tampon according to claim 1 wherein R is hydrogen and M is potassium.

110. The method of making a catamenial tampon which cornprises applying to a nonwoven cellulosic fabric a cross-limited polyacrylarnide polymer consisting essentially of the linear units:

wherein R is hydrogen or lower alkyl, Y is NH, or M0 and M is an alkali metal or ammonium, assembling a pad of alternate layers of said nonwoven fabric and of long staple oriented cotton fibers and compressing the resulting pad along the line of orientation of said cotton fibers to cylindrical form.

11. A method according to claim 10' wherein the polymer is applied to the nonwoven fabric in the form of an aqueous dispersion and the fabric is dried before assembly of said pad.

12. A method according to claim 10' wherein the polymer is applied to the nonwoven fabric by moistening the fabric, distributing the polymer thereon in powder form and drying the fabric before assembling said pad.

13. A method according to claim Ml wherein the nonwoven I fabric is bonded with an adhesive which is subsequently cured and the polymer is distributed on the fabric after application of the adhesive thereto and prior to curing of the adhesive. 

1. A catamenial tampon comprising a laminar pad compressed to cylindrical form, said laminar pad being composed of alternate layers of cotton and nonwoven cellulosic fabric, said nonwoven fabric layers having dispersed thereon an absorbency-improving additive which is a cross-linked polyamide consisting essentially of the linear units: and the cross-linking units:
 2. A catamenial tampon comprising compressed cellulosic fibers having incorporated therein an absorbency improving additive which is a cross-linked polyacrylamide consisting essentially of the linear units: and the cross-linking units:
 3. A tampon according to claim 1 wherein about 20 to 40 percent of the ''''Y'''' groups are MO groups and the remainder are NH2 groups.
 4. A tampon according to claim 3 wherein M is potassium.
 5. A tampon according to claim 2 wherein said additive is dispersed in said cellulosic fibers in powder form.
 6. A tampon according to claim 2 wherein said additive is dispersed in said cellulosic fibers in fiber form.
 7. A tampon according to claim 2 wherein said tampon is formed of laminations of cellulosic fibers and nonwoven fabric and said additive is incorporated in the nonwoven fabric.
 8. A tampon according to claim 2 wherein said additive is present to the extent of 2 to 15 percent by weight of said tampon.
 9. A tampon according to claim 1 wherein R is hydrogen and M is potassium.
 10. The method of making a catamenial tampon which comprises applying to a nonwoven cellulosic fabric a cross-linked polyacrylamide polymer consisting essentially of the linear units: and the cross-linking units:
 11. A method according to claim 10 wherein the polymer is applied to the nonwoven fabric in the form of an aqueous dispersion and the fabric is dried before assembly of said pad.
 12. A method according to claim 10 wherein the polymer is applied to the nonwoven fabric by moistening the fabric, distributing the polymer thereon in powder form and drying the fabric before assembling said pad.
 13. A method according to claim 10 wherein the nonwoven fabric is bonded with an adhesive which is subsequently cured and the polymer is distributed on the fabric after application of the adhesive thereto and prior to curing of the adhesive. 